As well known in the arts, a precision motor is usually provided in a data reading apparatus, e.g. a compact disc player. In general, this motor, as shown in FIG. 1, includes rotor members and stator members. The rotor members include a shaft 10, a rotor 12 and the magnet 14 therein. During operation, above mentioned three members proceed the high speed rotation along the axis of the shaft 10. The stator members include the coils 16, a base plate 17, a circuit board 18, a bush 19, a rear cap 15 and a pivot plate 13.
During operation of the motor, to prevent the detachment of rotor from the stator, in general, a retaining ring 11 is provided at the end of the shaft 10. This retaining ring 11 may attach to the shaft 10 by press fit relationship. Or, alternatively, by an engagement approach, the retaining ring 11 is engaged with a corresponding groove on the shaft 10.
Typically, the aforementioned shaft 10, rotor 12, magnet 14, coils 16, base plate 17, circuit board 18, bush 19 are first assembled together. Afterwards, the retaining ring 11 is disposed at the end of the rotor. In succession, the rear cap 15 is assembled to the pivot plate 13 such that the rear cap 15 is in press-fit with the base plate 17.
The retaining ring 11 may be in form of "C" shape with a narrow slot thereon. Alternatively, the retaining ring 11 may be in form of a press-fit closed ring. Due to the existence of the retaining ring 11 touching against the bushing 19 as the shaft 10 is pulled by an external force, the shaft 10 will not be pulled out of the motor. However, the retaining ring 11 is in high speed rotation together with the shaft 10. Therefore, should a small amount of eccentric phenomenon with regard to the weight distribution of the retaining ring 11 exists, adverse effect is imposed over the high speed rotation of the shaft 10.